Ultrasonic liquid atomizer with an improved soft start circuit

An apparatus for use with an ultrasonic liquid atomizer having a liquid chamber for holding liquid therein and a piezoelectric vibrator for generating pressure rises in said liquid in response to ultrasonic frequency energy, comprising:

• power supply means connected in use to a mains supply for generating a full-wave rectified supply voltage and a bias voltage with respect to a reference point;
• an oscillator having a first transistor connected to be biased by said bias voltage and a resonant circuit a part of which is formed by said piezoelectric vibrator, said transistor and said resonant circuit being connected to receive said full-wave rectified supply voltage to generate said ultrasonic energy in said piezoelectric vibrator in the presence of said bias voltage;
• and
• a soft start circuit including a first time constant circuit connected to said power supply means and a second transistor biased by the output of said time constant circuit, said second transistor providing switching action in phase with said full-wave rectified supply voltage so that the ultrasonic energy is generated in the form of a series of bursts having durations gradually increasing as a function of time during an initial brief interval from application of said bias voltage to said oscillator.

A combination comprising:

• an ultrasonic liquid atomizer having a liquid chamber for holding liquid therein and a piezoelectric vibrator for generating pressure rises in said liquid in response to ultrasonic energy and atomizing the liquid;
• voltage supply means connected in use to a mains supply and generating therefrom a full-wave rectified voltage;
• an oscillator having a bias terminal for generating said ultrasonic energy supplied with said full-wave rectified voltage;
• first means for periodically interrupting the supply of said full-wave rectified voltage to the bias terminal of said oscillator for variable lengths of time during an initial brief interval from application of said full-wave rectified voltage to the bias terminal of said oscillator so that the ultrasonic energy is generated in the form of a series of bursts which increase gradually in duration as a function of time during said initial brief interval;
• and
• second means effective upon the termination of said initial brief interval for preventing said first means from being affected by an unwanted voltage generated said oscillator.

A combination comprising:

• an ultrasonic liquid atomizer having a liquid chamber for holding liquid therein and a piezoelectric vibrator for generating pressure rises in said liquid in response to ultrasonic energy;
• a power circuit connected in use to a mains supply for generating a full-wave rectified supply voltage;
• a bias circuit connected to said power circuit for generating a bias voltage;
• an oscillator having a first transistor connected to be biased by said bias voltage and a resonant circuit a part of which is formed by said piezoelectric vibrator, said transistor and said resonant circuit being connected to receive said full-wave rectified supply voltage to generate said ultrasonic energy in said piezoelectric vibrator in the presence of said bias voltage;
• and
• a soft start circuit including a first time constant circuit connected to said bias circuit and a second transistor connected to be powered by said bias voltage and biased by the output of said time constant circuit, said second transistor providing switching action in phase with said fullwave rectified supply voltage so that the ultrasonic energy is generated in the form of bursts whose durations gradually increase as a function of time during an initial brief interval from application of said bias voltage to said oscillator.